DTC P0841: Transmission Fluid Pressure Sensor/Switch "A" Circuit Range/Performance: Notes

WARNING: This page is about a different car, the 2022 Subaru WRX. However, it is still accessible from the selected car via links, so may be relevant.

1. -

DTC detecting condition:

Detected when two consecutive driving cycles with fault occur.

Trouble symptom:

Acceleration is poor during standing start.
Shift control malfunction
Engine speed increases abruptly.

Wiring diagram:

CVT control system Ref. to WIRING SYSTEM>CVT CONTROL SYSTEM>WIRING DIAGRAM

Courtesy of SUBARU OF AMERICA, INC.

CAUTION:

Use CHECK BOARD when measuring the TCM terminal voltage and resistance.
After servicing or replacing faulty parts, perform the last step of the basic diagnostic procedure. Ref. to TRANSMISSION (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE

CHECK DTC .
Read the DTC of [Transmission] using the Subaru Select Monitor. Ref. to TRANSMISSION (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC)

Besides DTC P0841, is any of the DTC P0842 or P0843 displayed?

Yes : Perform the diagnosis according to DTC P0842 or P0843. Ref. to TRANSMISSION (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC)>LIST

No : Go to 2.
CHECK DTC .
Read the DTC of [Transmission] using the Subaru Select Monitor. Ref. to TRANSMISSION (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC)

Besides DTC P0841, is any of the DTC P0746 or P0747 displayed?

Yes : Perform the diagnosis according to DTC P0746 or P0747. Ref. to TRANSMISSION (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC)>LIST

No : Go to 3.
CHECK INPUT SIGNAL FOR TCM .
1. Turn the ignition switch to ON.
2. Using the Subaru Select Monitor, read data of [Line Pressure Sensor Voltage.] in the [Data Monitor] of [Transmission]. (While shaking the line pressure sensor harness) Ref. to TRANSMISSION (DIAGNOSTICS)>DATA MONITOR
Is [Line Pressure Sensor Voltage.] 0.39 - 0.61 V?

Yes : Go to 11.

No : Go to 4.
CHECK HARNESS .
CAUTION:
Start work after ATF cools down.
1. Turn the ignition switch to OFF.
2. Disconnect the TCM connector.
3. Remove the transmission oil pan.
4. Disconnect the line pressure sensor connector.
5. Measure the resistance between TCM connector and line pressure sensor connector.
  Connector & terminal
  
  (B67) No. 3 - (T35) No. 3:
  
  (B67) No. 4 - (T35) No. 2:
  
  (B67) No. 17 - (T35) No. 1:
Is the resistance less than 1 Ω?

Yes : Go to 5.

No : Repair the open circuit of harness.
CHECK HARNESS .
Measure the resistance between TCM connectors.

Connector & terminal

(B67) No. 3 - (B67) No. 17:

(B67) No. 4 - (B67) No. 3:

(B67) No. 17 - (B67) No. 4:

Is the resistance 1 MΩ or more?

Yes : Go to 6.

No : Repair the short circuit of harness.
CHECK HARNESS .
Measure the resistance between TCM connector and transmission body.

Connector & terminal

(B67) No. 3 - Transmission body:

(B67) No. 4 - Transmission body:

(B67) No. 17 - Transmission body:

Is the resistance 1 MΩ or more?

Yes : Go to 7.

No : Repair the short circuit of harness.
CHECK LINE PRESSURE SENSOR POWER SUPPLY .
1. Turn the ignition switch to ON.
2. Measure the voltage between TCM connectors.
  Connector & terminal
  
  (B67) No. 17 (+) - (B67) No. 3 (-):
Is the voltage 4.6 - 5.4 V?

Yes : Go to 8.

No : Check for poor contact of connector, and if no fault is found, replace the TCM. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>TRANSMISSION CONTROL MODULE (TCM)
CHECK LINE PRESSURE SENSOR POWER SUPPLY .
1. Turn the ignition switch to OFF.
2. Connect the line pressure sensor connector.
3. Turn the ignition switch to ON.
4. Measure the voltage between TCM connectors.
  Connector & terminal
  
  (B67) No. 17 (+) - (B67) No. 3 (-):
Is the voltage 4.6 - 5.4 V?

Yes : Go to 9.

No : Replace the control valve body. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>CONTROL VALVE BODY
CHECK LINE PRESSURE SENSOR OUTPUT .
Measure the voltage between TCM connectors.

Connector & terminal

(B67) No. 4 (+) - (B67) No. 3 (-):

Is the voltage 0.39 - 0.61 V?

Yes : Check for poor contact of connector, and if no fault is found, replace the TCM. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>TRANSMISSION CONTROL MODULE (TCM)

No : Go to 10.
CHECK CONNECTOR .
1. Turn the ignition switch to OFF.
2. Disconnect the TCM connector.
3. Disconnect the line pressure sensor connector.
4. Check the TCM connector (B67) and the line pressure sensor connector (T35).
Is the check result OK?

Yes : Go to 11.

No : Repair the connector, or replace harness.
CHECK TRANSMISSION FLUID .
1. Connect all connectors.
2. Check the amount of ATF. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>CVTF>INSPECTION
Is the check result OK?

Yes : Go to 12.

No : Adjust the amount of ATF. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>CVTF>INSPECTION Go to 12.
CHECK INPUT SIGNAL FOR TCM .
1. Start the engine.
2. Warm up until the ATF temperature reaches to 40 - 70°C (104 - 158°F).
3. Depress the brake pedal and move the select lever to each range at an interval of 5 seconds.
  NOTE:
  Move the select lever in the following order: "P" → "R" → "N" → "D" → "N" → "R" → "P".
4. Stabilize the engine speed at idle.
5. Using the Subaru Select Monitor, read data of [Actual line press.] in the [Data Monitor] of [Transmission]. Ref. to TRANSMISSION (DIAGNOSTICS)>DATA MONITOR
Is [Actual line press.] 0.5 - 1.5 MPa?

Yes : Go to 13.

No : Replace the control valve body. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>CONTROL VALVE BODY
CHECK INPUT SIGNAL FOR TCM .
1. Shift the select lever to "P" range.
2. Keep the engine speed at 3, 000 rpm.
3. Using the Subaru Select Monitor, read data of [Actual line press.] in the [Data Monitor] of [Transmission]. Ref. to TRANSMISSION (DIAGNOSTICS)>DATA MONITOR
Is [Actual line press.] 1.5 - 2.5 MPa? Is the difference between the actual oil pressure and the value measured in Step 12 0.2 MPa or more?

Yes : Replace the transmission assembly. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>TRANSMISSION ASSEMBLY

No : Replace the control valve body. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>CONTROL VALVE BODY